Treatment of shaped polyvinyl alcohol bodies



United States Patent This invention relates to a novel method fortreating shaped polyvinyl alcohol articles to increase their wet heatresistance and water repellency, and particularly to improve theirelastic properties.

It is well-known to improve the wet heat resistance of polyvinyl alcoholarticles and to insolubilize them by treating such articles with aqueoussolutions containing water-soluble aldehydes, particularly formaldehyde.When this acetalization procedure is applied directly to newly formedpolyvinyl alcohol fibers or articles, the acetalized fibers or articlesshrink or swell to a considerable extent in hot or boiling water,despite their incohol articles can be acetalized or ketalized with suchhigher aldehydes, ketones, acetals or ketals that are insoluble ordiflicultly soluble in water, preferably in aqueous medium by addingsurface active agents.

The different action of lower aldehydes and higher aldehydes is bestillustrated by the following table, which shows the results of theaction of various aldehydes on polyvinyl alcohol fibers having asoftening point in air of about 224 C. and in water of about 90 to 94 C.These fibers were obtained according to the method described in theapplication, Serial Number 300,375, noted previously.

In the table, the softening point is the temperature at which the fibershrinks 10 percent, and the softening point in Water is the temperatureof water in which the fiber shrinks 10 percent. The elastic recovery isthe recovery in percent of fiber length after the fiber had beenelongated by 1 percent and 3 percent, respectively, and released. Thewater repellency is measured by the length of time which the fiberfloats without sinking on the surface of water at room temperature. Thedegree of acetalization is defined by the ratio of the original hydroxylgroups acetalized by the aldehyde treatment.

TABLE Softening Point; in- Shrinkage in Tensile strength Elasticrecovery after elongation Test N0. Aldehyde Degree of of Water Aeetali-Water, Air, Water of Air of Dry, Wet, Wet/dry, repellency zation,percent percent 100 (3., 200 0., gr./d. gn/d. percent mol percentpercent 1% 3% percent 1 Formaldehyde 12.2 95 216 54. 7 7.0 2.04 1. 3365. 3 72 54 0.3 min. 2 d0 27. 9 100 219 5. 3 5. 5 2.11 1. 64. 5 81 520.4 min. 35. 3 100 216 4. 2 6.0 2. 09 1. 26 60. 5 83 57 0.5 min. 41. 5100 217 3.1 5.0 2.06 1. 32 64. 2 82 56 0.5 min. 33. 8 100 214 6.0 7.0 1.87 0.62 32. 9 83 56 3.0 min. 45.1 100 205 5. 3 9. 0 2. 19 0.89 40. 8 8754 4 0 min. 7 26. 0 100 202 7.0 9. 8 2. 42 1. 54 63. 8 100 61 1200 min 8o 35. 2 100 196 12.0 13. 4 2.18 1. 44 66.0 99 66 1400 min. 9Isovaleraldehyde 26. 4 100 198 12.5 13. 8 2. 20 1. 61 73.0 95 64 Manydays. 10 do 30.2 100 138 10.0 15. 2 2.19 1. 55 70. 8 100 66 D0. 11Heptaldehyde 14.3 100 214 12. 0 6. 1 2. 35 1. 28 54.0 92 58 D0. 12.Benzaldehy de 15. 1 100 204 43. 5 6. 3 2. 82 1. 51 53. 7 96 65 D0. 13. o30.7 100 200 6.0 10.0 2.08 1. 72.1 98 77 Do. 14-..- o 41.0 100 180 9.219.0 1.85 1.35 72.6 100 82 D0. 15 p-Tolylaldehyde 20. 2 100 200 5. 510.0 2.10 1. 38 65. 6 98 68 Do. 16 o-Chl0robenzaldehyde 22. 7 100 1989.0 16. 8 1. 93 1. 31 67. 5 98 82 D0. 17 m-Nitrobenzaldehyde 30. 6 100195 3. 8 12.0 1. 74 1. 34 77.0 97 77 Do. 18 p-Cyanobenzaldehyde. 34.3100 187 5. 8 14. 0 1. 82 1. 28 70.3 97 85 Do. 19 Salicylaldehyde 12.2100 223 6. 6 4.0 1. 52 1. 26 75. 4 93 72 Do.

solubilization, and the heat resistance is considerably decreased. Ifthis treatment is applied to polyvinyl al cohol fibers or articles whichhave been previously made more water resistant by a heat treatment,their shrinking or swelling in hot or boiling water is so much reducedas to render such heat-treated fibers and articles suitable forpractical use, whereby the good heat resistance remains substantiallyunchanged, as disclosed and claimed in the patent application, SerialNumber 300,375 by T suklnno Tomonari and Shigeki Nomura, filed July 23,1952, and which is now Patent No. 2,990,235, which is acontinuation-in-part of patent application Serial Number 154,873, filedApril 8, 1950, now abandoned.

We have found that a treatment of heat-treated polyvinyl alcoholarticles with aldehydes and ketones having at least 4 carbon atoms, orwith acetals and ketals thereof with lower alcohols such asmethylalcohol, ethylalcohol, propylalcohol, ethylene glycol, and thelike, imparts to such articles properties, particularly excellentelastic recovery or resiliency and water repellency, which cannot beobtained by a treatment with formaldehyde or The table shows that theheat and wet heat resistance is most effectively improved by a treatmentwith formaldehyde and decreases slightly when higher aldehydes are used.The latter, however, improve considerably the w elastic recovery andespecially the Water repellency. It

is to be noted that this improvement is already conspicuous atrelatively low acetalization degree.

According to A. Weihe Kunststoffe, vol. 31, page 53 (1941), thesoftening point of polyvinyl acetals with various aldehydes is shown inthe following table:

[Softening points in 0.]

Polyvinyl alcohol-formaldehyde acetal A polyvinyl alcohol fiber consistsof amorphous and readiy accessible parts, and of crystalline andinaccessible or difiicultly accessible parts. When such a fiber isacetal- Patented June 16, 1964,

ized the reaction will proceed mainly in the amorphous parts at theearly stages of acctalization and will then slowly extend into thecrystalline parts. If the acctalization is applied to newly spun fibers,which were not subjected to a heat treatment, the original crystallineparts become easily accessible during the reaction, and consequently,the softening point in air of the acetalized fiber decreasesconsiderably and approaches the value shown by Weihe as theacctalization proceeds. The softening point in water of the partiallyacetalized fiber is also insuflicient, because of the presence of theremaining accessible hydroxyl groups. When a heat-treated fiber isacetalized, the original crystalline parts remain generally inaccessibleunder conventional treating conditions, and the decrease of thesoftening point in air is not so great. The softening point in water ofthe acetalized fiber reaches easily 100 C. because of the absence of theaccessible hydroxyl groups and because of the higher heat resistance inair.

Representative examples of suitable aldehydes, ketones, acetals andketals are n-butyraldehyde, isobutyraldehyde, valeraldehyde,isovaleraldehyde, capronic aldehyde, heptaldehyde, caprylic aldehyde,undecylaldehyde, lauric aldehyde, palmitic aldehyde, stearic aldehyde,oleic aldehyde, alpha-ethyl-beta-propylacrolein, benzaldehyde,tolylaldehydes, phenylacetaldehyde, cinnamic aldehyde, naphthaldehydes,anisaldehyde, furfural, tetrahydrofurfural, chlorobenzaldehydes,methoxybenzaldehydes, nitrobenzaldehydes, salicylaldehyde,oxynaphthaldehydes, thiophenaldehyde, cyanobenzaldehydes, terephthalicacid aldehydes, phenoxypropionic aldehyde, nitrophenoxyacetaldehydes,chlorophenoxyacetaldehydes, hexahydrobenzaldehyde, etc.; acetophenone,benzophenone, tetrahydroquinone, cyclohexanone, nitrocyclohexanones,chlorocyclohexanones, etc.; and their acetals and ketals with loweralcohols. Also mixtures of these compounds may be used.

These higher aldehydes, ketones, acetals and ketals are insoluble oronly sparingly soluble in water. For example, the solubility in water ofvarious aldehydes at room temperature is shown as follows:

Formaldehyde oo. Acetaldehyde co. Propionaldehyde 16.2%. Butyraldehyde3.7%. Valeraldehyde 0. Acetaldehyde-diethylacetal 4.6%. Benzaldehyde0.33%. Cyclohexanone slightly.

They are preferably applied in the form of an aqueous emulsion whichcontains about 0.5 to percent of them, in the presence of an acid or anacid and a salt.

In order to emulsify these compounds in water, surface active agents areused, and the selection of the suitable type of surface active agent, orof a mixture of such agents, will depend on the nature of theacetalizing or ketalizing compound and on the other components of theacetalizing bath in which it should be stable. We may use either anionactive agents, such as sulfuric esters of fatty alcohols, alkanesulfonates, alkyl-aromatic sulfonates, sulfonated esters, or cationactive agents such as quaternary ammonium salts, pyridinium salts,piperidinium salts, morpholinium salts, amino alcohol derivatives, ornonionic agents, such as polyoxyethylene ethers of high molecular weightaliphatic alcohols or alkyl phenols, aliphatic fatty acid esters ofpolyethylene glycol, sorbitan derivatives, and the like.

The acctalization or ketalization in the form of an aqueous emulsion isnot only inexpensive but also proceeds rapidly as compared with that inan organic solvent solution.

The acctalization or ketalization bath may contain the conventionalacids as catalysts or such acids and salts to prevent excessive swellingof the polyvinyl alcohol articles. As acids we may use inorganic acids,such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoricacid, or mixtures of such inorganic acids and water soluble organicacids having less than five carbon atoms; also mixtures of these acidscan be used, and the concentrations may vary within wide limits fromabout 0.1 to 25 percent based on weight of the bath. The salts will be,in general, a salt or a mixture of salts of the acid used, and the bathmay contain up to about 25 percent by weight of such salts.

The acctalization or ketalization rate and degree can be controlled to acertain extent by the composition of the acetalizing bath and thetemperatures and times of reaction. In general, the reaction rate isincreased by increasing temperatures, increasing aldehyde or ketoneconcentration, increasing acid concentration, and decreasing saltconcentration.

The speed and degree of reaction depend also on the properties andhistory of the articles to be acetalized. If the article had beenheat-treated, the acetalization reaction is retarded, depending on thedegree of insolubilization obtained. vinyl alcohol article has raisedits softening temperature in Water to 80-96" C., the acetalization withhigher aldehydes proceeds rather slowly to a limited degree. This is notobjectionable because we prefer to apply our novel acctalization methodto polyvinyl alcohol articles which are already fairly water resistant.The articles should not be soluble in water of less than C. and shouldshrink or elongate in water of 50 C. by not more than 20 percent in anydirection. With respect to fibers, we prefer to use fibers which shrinkin water of C. by not more than 5 percent of their length. Under theseconditions, a relatively low acctalization or ketalization with higheraldehydes or ketones is sufiicieut to attain the desired improvedelastic recovery, water repellency and sufficient heat resistance in airand water desired for practical use. A very excessive acctalization orketaliza tion under severe conditions should be avoided in order toprevent a harmful decrease of the heat resistance.

As explained above, the softening temperature of homogeneous polyvinylalcohol acetals of higher aldehydes is low but it is high forheterogeneous articles, such as fibers which were coagulated and spunfrom an aqueous polyvinyl alcohol solution, dried and heat-treatedbefore acctalization. The elastic properties of such fibers acetalizedin accordance with the invention compare favorably with those of wool.

The table given above shows that the acctalization with formaldehydeimproves the heat and wet heat resistance of polyvinyl alcohol articles,whereas acetalization with higher aldehydes improves the elasticrecovery and water repellency. Therefore, a modification of ourinvention consists in combining the two acctalization procedures so asto obtain a polyvinyl alcohol article having a high softening point inair and water as well as good elastic properties and water repellency.This can be accomplished by using a single acctalization bath containingformaldehyde and a higher aldehyde, acetal, ketone, or ketal or bysubjecting the article to successive treatments in Whatever order.

We have described our new process with respect to polyvinyl alcoholfibers, but it can be applied also to other shaped polyvinyl alcoholarticles such as bristles, films, sheets, plates, ribbons, rods, and thelike.

The following illustrative examples are given to show our novelacetalizing method, and are not intended to limit the invention in anyway. All figures are given by weight, unless stated otherwise.

In order to obtain comparative figures for the various.

and a softening point in water of C. to 91 C. The

fiber was obtained according to the process of patent application,Serial Number 300,375, mentioned above, by

If the preceding heat treatment of the polyspinning an aqueous polyvinylalcohol solution into a salt bath, stretching the filaments andheat-treating them at 225 C. It is to be understood that similar resultswith respect to elastic recovery and Water repellency in additests 5% offormaldehyde and 15% of sodium sulfate. The only variable was theconcentration of sulfuric acid in the formaldehyde bath, and thefollowing table shows its influence on the acetalization degrees,shrinkage and elastion to suflicient heat resistance in air and waterare ob- 5 tic recovery of the fibers after the treatment in both baths.

Acetalization Degree Percent Shrinkage Elastic Re- H2SO4 covery after inCHZO elongation of bath, 111 In In water In air percent CHzO GsH CHOTotal of 100 C. of 200 C.

2 3. 6 30. 5 34.1 18.0 16 99 69 5 13. 4 25. 3 as. 7 s. s 14 9s 64 7 20.6 15. 4 .36. 4.8 s 96 5s a0. 2 5. 4 35.6 a. 2 6 96 53 tained withpolyvinyl alcohol fibers or shaped articles pre- Example 4 pared byother methods.

Example 1 Fibers were subjected for 60 minutes at 60 C. to the action ofan aqueous bath containing 2% of benzaldehyde, 5% of sulfuric acid, andvarying amounts of methanol or various surface active agents. Theresults of the tests are given in the table below.

Surface Degree of Shrinkage Tensile Methanol, percent Active Acetaliinwater Strength,

Agent zation of 100 C. g./den. in percent in percent The fiber definedabove was acetalized for 1 hour at 70 C. in an aqueous solutioncontaining 5% of sulfuric acid, 0.3% of a fatty alcohol sulfate, and 3%of formaldehyde as well as 1% of benzaldehyde. The shrinkage of theacetalized fiber was 4.7% in water of 100 C. and 4.5% in air of 200 C.The elastic recovery was 99% after 1% elongation and 66% after 3%elongation.

The fiber was first acetalized for one hour at 60 C. in ano-chlorobenzaldehyde bath containing 2% of o-chlorobenzaldehyde, 5% ofsulfuric acid, and 1.5 of fatty alcohol sulfate, and then for one hourat 70 C. in an aqueous formaldehyde solution containing 5% offormaldehyde, 10% of sulfuric acid, and 15% of sodium sulfate. The thusacetalized fiber had a shrinkage of 5% in water of 100 C. and ashrinkage of 5.5% in air of 200 C.; its elastic recovery was 97 after 1%elongation and 61 after 3% elongation.

Example 5 The fiber was ketalized first for 1 hour at 70 C. in anaqueous emulsion containing 5% of cyclohexanone, 15% of sulfuric acid,5% of sodium sulfate, and 3% of Nacconol NR. Subsequently, it wasacetalized for 30 minutes at 60 C. in an aqueous solution containing 3%of formaldehyde, 10% of sulfuric acid, and 10% of sodium sulfate. Theobtained fiber had excellent water resistance, heat and wet heatresistance, and elastic recovery properties.

Example 6 Fibers were acetalized for 1 hour at 60 C. in the followingfour different solutions.

(1) 1% of butyraldehyde, 5% of sulfuric acid, 5% of sodium sulfate, 2%of dodecyl benzene sulfonate; (2) 2% of isovaleraldehyde, 10% ofsulfuric acid, 1.5%

of fatty alcohol sulfates;

(3) 2% of heptaldehyde, 5% of sulfuric acid, 2% of polyethyleneglycololeate;

(4) 2% of benzaldehyde, 5% of sulfuric acid, 2% of polyethyleneglycolether of alkyl phenol.

The resulting properties of the obtained fibers are shown in thefollowing table:

Softening Point Tensile strength Elastic Degree in in g./d. RecoveryWater of Acct- Repellcncy alization Water Air Dry Wet 1% el. 3% el.

1 26. 0 100 202 2. 42 1. 54 100 61 1,200 min. 2 30.2 100 188 2.19 1. 10066 Many days. 3 14. 3 100 214 2. 35 1. 28 92 58 Do. 4 30. 7 100 200 2.08 1. 50 98 77 Do.

Example 3 Example 7 The fiber was first acetalized at a temperature of70 C. for one hour with formaldehyde, and subsequently at C. for onehour with benzaldehyde. Four comparative tests were made. Thebenzaldehyde bath had in all four tests the same composition andcontained 2% of benzaldehyde, 5% of sulfuric acid, and 1% of a fattyalcohol sulfate. The formaldehyde bath contained in all 75 3% The fiberwas acetalized for 1 hour at 60 C. in an aqueous bath containing 2% ofheptaldehyde and 5% of sulfuric acid emulsified with a mixture of 1% ofsorbitan laurate and 1% of dodecylbenzene sulfonate. The acetalizationdegree of the obtained fiber was 15%, the shrinkage in boiling water9.0%, the softening point in air 215 C., and the elastic recovery at 1%elongation 92% and at elongation 56%.

If the same fiber was acetalized under the same conditions in anemulsion containing 3% of alpha-ethyl-betapropyl acrolein, 10% ofsulfuric acid and 1.5% of fatty alcohol sulfate, the acetalizationdegree was 12% and the properties similar to those of the fiberacetalized with heptaldehyde. Both fibers showed excellent waterrepellence and remained for many days unwetted by water.

Example 8 The following emulsions were used to acetalize polyvinylalcohol fibers, under the same conditions as stated hereinbefore.

(1) 3% of naphthaldehyde, of sulfuric acid, 2% of fatty alcohol sulfate;

(2) 3% of cinnamicaldehyde, of sulfuric acid, 2%

of alkylaryl sulfonate;

(3) 4% of phenylacetaldehyde, 7% of sulfuric acid, 3%

of Nacconol NR.

In all three cases, the fibers had excellent water repellent and elasticrecovery properties.

Example 9 Heat-treated polyvinyl alcohol fibers were acetalized for 1hour at 65 C. in the following aqueous solutions:

( 1) 2% of o-chlorobenzaldehyde, 10% of sulfuric acid,

40% of methanol;

(2) 1.3% of o-chlorobenzaldehyde, 2.5% of sulfuric acid,

0.5% of fatty alcohol sulfate;

(3) 1.3% of rn-nitrobenzaldehyde, 2.5% of sulfuric acid,

0.5% of fatty alcohol sulfate;

(4) 1.3% of p-chlorobenzaldehyde, 3% of sulfuric acid,

0.5% of fatty alcohol sulfate.

The following table shows degrees of acetalization and properties of theobtained fibers:

Degree of Shrinkage Elastic recovery, in per- Anetalizain water cent,after elongation of Lion in mol of 100 0. percent in percent Example 10A polyvinyl alcohol bristle having a diameter of 0.5 mm. was stretchedfor 1 minute at 150 C. to 2.5 times its original length (I), and thenheat-treated for 1 minute at 220 C. (II). I and II were acetalized for 1hour at C. in a bath consisting of 2% of o-chlorobenzalde- 'hyde, 2% ofsulfuric acid, 1% of fatty alcohol sulfate and 95% water (III) and (IV)respectively.

The dry and wet heat resistances of these bristles are shown in thefollowing table:

() =Elongat-ion.

The results show that the bristle acetalizcd after heattreatment hadbetter dry and wet heat resistances than the bristle acetalized withoutprevious heat-treating.

The bristle acetalizcd with o-chlorobenzaldehyde after heat-treatment(IV) had more excellent elastic properties 8 Example 11 A polyvinylalcohol film having a thickness of mm. was made by evaporating anaqueous polyvinyl alcohol solution (I). The film was heat-treated for 3minutes at 205 C. (II). I and II were acetalized for 20 minutes at 50 C.in a bath containing 2% of m-nitrobenzaldehyde, 2% of sulfuric acid and1% of fatty alcohol sulfate, (III) and (1V), respectively. III isdissolved in the bath during acetaliza'tion. The resistance in water ofthe films I, II and IV is shown in the following table.

[Elongation in percent] In water or 1 In water of 5 In water of 7 Inwater of 8 In water of 9 The film acetalized with m-nitrobenzaldehydeafter heattreatment had better elastic properties than that formalized.

We have found that a polyvinyl alcohol fiber or a shaped polyvinylalcohol body which was treated with a compound selected from the groupconsisting of aldehydes, ketones having at least four carbon atoms andacetals thereof, have improved properties not only as to their hot-waterresistance and heat resistance but also with respect to theirresilience, especially at a high elongation degree, when said treatmentis applied after, simultaneously with, or before a treatment of thearticle with one or more compounds selected from the group consisting ofdialdehydes, aldehyde-ketones and acetals thereof.

Example 1 2 A polyvinyl alcohol fiber made by wet spinning process washeat-treated for 3 minutes at 220 C. (I) and then treated for 1 hour at70 C. in an aqueous emulsion containing 1 percent ofo-chlorobenzaldehyde, 3 percent of sulfuric acid and 1 percent of sodiumsalt of alkyl benzene sulfonic acid (II). The fibers I and II weretreated for 1 hour at 70 C. in an aqueous solution containing 10 percentof sulfuric acid, 10 percent of sodium sulfate and 0.3 percent ofterephthalic aldehyde (III and IV, respectively) The dry and wet heatresistance and the elastic recovery of the fibers, H, III and IV, andthe elastic recovery of wool are shown in the following table. The dryheat resistance is illustrated by the softening temperature C.) in air,and the wet heat resistance is shown by the shrinkage (percent) whentreated in boiling Water for 1 hour.

II III IV Acetalizcd Acetalized with owith o- Aeetalizcdehlorochlorowith tcrbenzalde- Wool benzaldcephthalic hydc and hydealdehyde terephthalic aldehyde Softening temp. in air 190 225 Shrinkagein boiling water (percent) 7.0 0.1 Elastic recovery (percent):

t 1% cl0ngation 100 92 100 99 At 2% elongatiorn 9D 83 96 03 At 3%elongatiom 77 82 S7 87 At 5% elongatiom 52 71 75 At 7% elongatiom 41 8O60 62 At 10% elongation. 35 78 50 48 (IV) is excellent with respect toelastic recovery in the range of 1 to 10 percent elongation and itselastic recovery is fully comparable to that of wool.

In addition, the results show that the dry and Wet heat resistance ofthe fiber acetalized with o-chlorobenzaldehyde (II) is considerablyimproved by the additional acetalization with terephthalic aldehyde.

Example 13 A fiber heat-treated as in Example 12 was treated for 1 hourat 70 C. in an aqueous solution containing 2% of glyoxal, 15% ofsulfuric acid, and 15% of sodium sulfate. Subsequently, it was treatedfor 1 hour at 60 C. in an aqueous solution containing 1% ofn-butyraldehyde, 10% of sulfuric acid, and 10% of sodium sulfate.

The obtained fiber had a shrinkage of merely 2.5% after a treatment for1 hour in boiling water and a softening temperature of 200 C. in air,its elastic recovery was excellent up to high elongation, like the fiberof the preceding example.

Example 14 A fiber heat-treated as in the preceding examples was treatedfor 1.5 hours at 60 C. in an aqueous solution containing 0.5% ofiso-butyraldehyde, 2% of glyoxal, 15 of sulfuric acid, and 15 of sodiumsulfate.

The obtained fiber had excellent Water resistance, heat and wet heatresistance, and elastic recovery properties.

Example 15 A polyvinyl alcohol film prepared by evaporation of anaqueous polyvinyl alcohol solution and treated for 10 minutes innitrogen gas of 200 C., was treated for 1 hour at 60 C. in an aqueousemulsion containing 2% of n-octylaldehyde, of sulfuric acid, and 2% offatty alcohol sulfate, and subsequently for 1 hour at 70 C. in anaqueous solution containing 0.3% of terephthalic aldehyde, of sulfuricacid, and 10% of sodium sulfate.

The obtained film had better heat resistance, hot-water resistance, andelastic recovery properties than a film which was acetalized byn-octylaldehyde only.

The term polyvinyl alcohol as used in the specification and claims is tobe understood to refer not only to polyvinyl alcohol proper but also toits copolymers with other polymerizable compounds, such as ethylene,maleic anhydride, acrylonitrile, and the like, provided such copolymerscontain at least 80 percent by weight of polyvinyl alcohol. Suchcopolymers are known in the art and are used for the preparation of thesame articles, particularly fibers, in the same way as polyvinylalcohol.

This application is a continuation of application Serial Number 340,922,filed March 6, 1953 of Tetsuro Osugi,

l0 Masakazu Matsumoto, Kenichi Tanabe and Yasuji Ohno, now abandoned.

We claim:

1. The method of improving the properties of polyvinyl alcohol fibersand films which comprises acetalizing previously-formed polyvinylalcohol fibers and films which shrink not more than 5% in length in 80C. water by reaction with an aqueous acidified dispersion containing atleast one surface active agent and about 0.5 to 15% by weight of adispersed reactant selected from the group consisting of benzaldehydeand acetals thereof formed with lower alcohols having up to 3 carbonatoms, the total degree of acetalization of the fibers and films notexceeding and the degree of acetalization with said reactant being atleast 5%, said reactant being at most sparingly-soluble in water.

2. The method of claim 1 wherein said reactant is benzaldehyde.

3. The method of claim 1 wherein the acetalization reaction is carriedout at about 40 C. to C. for about 1 to 2 hours.

4. The method of claim 1 wherein the fibers and films are acetalized bythe said reactant and also by formaldehyde.

5. The method of claim 1 wherein the fibers and films are acetalized bythe said reactant and also by a dialdehyde.

6. The method of claim 1 wherein the fibers and films are acetalized bythe said reactant and also by a ketoaldehyde.

References Cited in the file of this patent UNITED STATES PATENTS2,072,302 Hermann et a1. Mar. 2, 1937 2,310,943 Dorough et a1. Feb. 16,1943 2,327,872 Dahle Aug. 24, 1943 2,380,033 Dorough et al July 10, 19452,610,360 Cline et a1. Sept. 16, 1952 2,636,803 Cline et a1 Apr. 28,1953 2,636,804 McCleltan et al Apr. 28, 1953 2,668,803 Lantz Feb. 9,1954 2,977,183 Osugi et a1. Mar. 28, 1961 2,990,235 Tomonari et a1 June27, 1961 FOREIGN PATENTS 459,878 Great Britain J an. 18, 1937 OTHERREFERENCES Sakurada: Bull. Inst. Phys. Chem. Research (Tokyo),

1942, 21, 1077-1083 (through Chem. Abstr. 1948, 42, 1780d). (Copy inJournal Textile Inst, June 1948, page A 316.)

UNITED STATES PATENT OFFICE CETIFICATE ()F' CORRECTION Patent No. 3 137540 June 16 1964 Tetsuro Osugi et 2110 It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column line 75, after "properties" insert than that formalized,

Signed and sealed this 10th day of November 1964 (SEAL) Attest:

ERNEST Wa SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. THE METHOD OF IMPROVING THE PROPERTIES OF POLYVINYL ALCOHOL FIBERS NDFILMS WHICH COMPRISES ACETALIZING PREVIOUSLY-FORMED POLYVINYL ALCOHOLFIBERS AND FILMS WHICH SHRINK NOT MORE THAN 5% INLENGTH TO 80*C. WATERBY REACTION WITH AN AQUEOUS ACIDIFIED DISPERSION CONTAINING AT LEAST ONESURFACE ACTIVE AGENT AND ABOUT 0.5 TO 15% BY WEIGHT OF A DISPERSEDREACTANT SELECTED FROM THE GROUP CONSISTING OF BENZALDEHYDE AND ACETALSTHEREOF FORMED WITH LOWER ALCOHOLS HAVING UP TO 3 CARBON ATOMS, THETOTAL DEGGREE OF ACETALIZATION OF THE FIBERS AND FILMS NOT EXCEEDING 50%AND THE DEGREE OF ACETALIZATION WITH SAID REACTANT BEING AT LEAST 5%,SAID REACTANT BEING AT MOST SPARINGLY-SOLUBLE IN WATER.